This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A fascinating problem in biology is, how plants control the structure of their cell walls during growth on a molecular level. We propose to probe the cellulose structure in genetically modified plants, in plant parts such as stems or roots which grow significantly faster than in the wildtype. We obtained first results with wide-angle scattering/fiber diffraction on D-line in the last run, however, the data were limited by background levels and the limited detector area and resolution. At F1 we would like to use the helium environment developed for the protein microcrystallography effort, in combination with either a 100 micron collimator or a focusing capillary. Goal of this development study is to see, which features are essential to the success of this experiment where we would like to obtain as detailed data on the cellulose structure as possible (helium, prewetted helium at room temperature, dry helium for cryogenic temperature, detector range, signal-to-noise).